Modern vehicles frequently include vehicle telematics units that are capable of wirelessly communicating both voice and data between vehicles and central facilities. These communications involve wireless carrier systems and are frequently carried out using circuit-switched telephone calls. However, these and other types of telephone calls can pass through an increasing number of switches and/or telephony infrastructure before ultimately arriving at their destination. The increase in communication infrastructure complexity is often accompanied by an increase in transmission costs—an increase that can be amplified depending on other factors, such as whether the vehicle is operating on a roaming network or communicating both voice and data. This increase in complexity can also make the communications vulnerable to eavesdropping.